Certain bacteria regulate gene expression in a density-dependent manner, a phenomenon referred to as "quorum sensing". One of the key regulatory proteins in the quorum response pathway is ComS, which controls the expression of genes involved in fatty acid metabolism, genes known to be regulated by the alternate sigma factor sigma-H, and the putative transcription factor LrpC. The overall focus of this proposed research is to characterize the regulatory pathways controlled by ComS with an emphasis on possible connections between the quorum response and regulated proteolysis. A global approach will be used to determine the role of ComS in regulating expression of IrpC by identifying the step at which the expression of IrpC is affected by ComS, characterizing cis- and trans-acting factors that affect lrpC expression, and determining whether LrpC negatively affects its own expression in a ComS-dependent manner. A mechanistic approach will be used to determine whether the stability of key regulatory proteins is controlled by ComS and, if so, I will characterize how ComS affects proteolysis of these proteins. Understanding the regulatory pathways governing the quorum response will aid in our better understanding of how bacteria communicate with one another.